The present disclosure relates to a device and method for processing images.
Electronic devices such as digital still cameras are capable of recording digital data of captured images. Such an electronic device includes an image processing device that converts the digital data of the captured image into a certain format. The image processing device performs image processing such as a sensor linearity correction. The sensor linearity correction is performed by executing, for example, a correction process (LUT correction process) that uses a lookup table (LUT). The LUT is a table illustrating output values (corrected data) corresponding to values input at specific intervals. The use of the LUT allows for non-linear properties, which are difficult to express with a mathematic expression, to be expressed. In the LUT correction process, for example, the input value is input as an address value of a RAM, which stores the LUT, and the output value corresponding to the address value is output as the corrected data to execute LUT correction (sensor linearity correction) on the input value.
FIG. 20 illustrates one example of an LUT correction unit 200 that performs the sensor linearity correction on image data of a Bayer arrangement output from an image sensor such as a CCD or a CMOS.
Due to the increase in the processing speed of image sensors, the LUT correction unit 200 is provided in parallel with plural pieces of pixel data SB each included in line data for a plurality of lines (four lines in the illustrated example) of the image data. The LUT correction unit 200 includes LUT sections 202A to 202D respectively for the lines to perform the sensor linearity correction (LUT correction process) on the pixel data SB for each line and output corrected pixel data SG. The LUT sections 202A to 202D each include a RAM storing a correction curve for the sensor linearity correction. The correction curve indicates the properties of the output value (sensor-linearity corrected pixel value) corresponding to the input value, and a dedicated correction curve is prepared for each color component. In other words, as illustrated in FIG. 21, a correction curve for red (R) component pixel data (R pixel), a correction curve for green (G) component pixel data (G pixel), and a correction curve for blue (B) component pixel data (B pixel) are prepared. In the image data of the Bayer arrangement, for example, R pixels and G pixels are alternately arranged in the line data of the first line and the third line, and G pixels and B pixels are alternately arranged in the line data of the second line and the fourth line. Thus, the LUT sections 202A and 202C, to which the line data of the first line and the third line are provided, respectively include RAMs 205A and 205C, which store the correction curve for the R pixels, and RAMs 206A and 206C, which store the correction curve for the G pixels. The LUT sections 202B and 202D, to which the line data of the second line and the fourth line are provided, respectively include RAMs 205B and 205D, which store the correction curve for the B pixels, and RAMs 206B and 206D, which store the correction curve for the G pixels.
In each of the LUT sections 202A to 202D, for example, the pixel data SB is provided as the address value of the RAMs 205A to 205D and 206A to 206D, and the output value corresponding to the address value is output to a selection circuit 207. In the LUT sections 202A to 202D, the selection circuit 207 selects the output values of the RAM 205A to 205D or the output values of the RAM 206A to 206D, and the selected output value is output as the sensor-linearity-corrected pixel data SG.
Literature related to the above-described related art include Japanese Laid-Open Patent Publication No. 6-70165 and Japanese Laid-Open Patent Publication No. 2007-293827.